The Spinal Cord - Anatomy, Pathways, and Disorders

Vocabulary practice flashcards covering spinal cord anatomy, fiber types, nerve roots, ascending and descending pathways, reflex arcs, and common spinal cord disorders.

Spinal Cord

A major component of the central nervous system (CNS) extending from the brainstem through the vertebral column, weighing about $35\,\text{g}$ and measuring approximately $1\,\text{cm}$ in diameter.

Vertebral Column Protection

The bony protection provided by 26 vertebrae separated by cushioning cartilage discs that surround and safeguard the spinal cord from mechanical injury.

Meningeal Layers

The three protective membrane layers (Dura mater, Arachnoid, and Pia mater) that enclose the spinal cord within the vertebral column.

Spinal Cord Sections

The five regional divisions of the spinal cord housed in the vertebral column: cervical, thoracic, lumbar, sacral, and coccygeal sections.

General Somatic Efferent (GSE) Fibers

Efferent motor nerve fibers that transmit signals from the central nervous system to skeletal muscles.

General Visceral Efferent (GVE) Fibers

Efferent motor nerve fibers that convey signals to smooth muscle, the heart, and glands.

General Somatic Afferent (GSA) Fibers

Afferent sensory nerve fibers that transmit sensory information from the skin back to the central nervous system.

General Efferent Afferent (GVA) Fibers

Afferent sensory nerve fibers carrying sensory information from visceral organs like the lungs and digestive tract.

Dorsal Root

The nerve root that brings sensory (afferent) input into the central nervous system.

Ventral Root

The nerve root that transmits motor (efferent) commands out from the central nervous system to effector organs.

Dorsal Ramus

A peripheral branch of a mixed spinal nerve that supplies sensory and motor innervation to the back.

Ventral Ramus

A peripheral branch of a mixed spinal nerve that supplies sensory and motor innervation to the anterolateral trunk and limbs.

Dorsal Column Medial Lemniscus (DCML) Pathway

An ascending sensory pathway carrying fine touch, vibration, and conscious proprioception; first-order fibers enter via the dorsal root ganglion, ascend ipsilaterally, and decussate in the medulla.

Romberg Sign

A positive clinical finding indicating a loss of vibration/position sense due to damage in the DCML pathway.

Spinothalamic Tract

An ascending pathway carrying pain, temperature, and crude touch sensations that synapses in the dorsal horn and decussates in the spinal cord within 1–2 segments to ascend contralaterally.

Spinocerebellar Tracts

Ascending sensory pathways that convey unconscious proprioceptive information to the cerebellum for postural control and movement coordination.

Lateral Corticospinal Tract

A major descending motor system responsible for skilled voluntary movement of the limbs, decussating at the pyramidal decussation.

Anterior Corticospinal Tract

A descending motor pathway that contributes mainly to axial and trunk muscle control.

Vestibulospinal Tract

An extrapyramidal motor tract that maintains balance and promotes extensor tone.

Rubrospinal Tract

An extrapyramidal motor tract involved in regulating flexor tone.

Reflex Arc

A neural circuit within the spinal cord that controls rapid, automatic responses to stimuli (such as the knee-jerk reflex) without requiring initial processing by the brain.

Spinal Cord Injury (SCI)

Damage to the spinal cord, frequently caused by traumatic events like vehicular accidents (which account for $40\%$ of cases), leading to complete or incomplete paralysis/weakness.

Paraplegia and Paraparesis

Complete loss of movement (paraplegia) or weakness (paraparesis) affecting the legs due to spinal cord damage.

Quadriplegia and Quadriparesis

Complete loss of movement (quadriplegia) or weakness (quadriparesis) affecting all four limbs (arms and legs).

Spina Bifida

A developmental neural tube defect occurring in the womb that affects the lower spinal cord, potentially causing paraparesis alongside bowel and bladder dysfunction.

Poliomyelitis

An inflammatory disease of the spinal cord affecting gray matter, leading to motor loss.

Leukomyelitis

An inflammatory disease of the spinal cord affecting white matter, leading to sensory loss.

Transverse Myelitis

An inflammatory condition of the spinal cord affecting both gray matter and white matter, resulting in both motor and sensory deficits.

Peripheral Neuropathy

Inflammation and degeneration of nerves in the peripheral nervous system (commonly the feet) caused by diabetes, toxins, infections, or nutrition, leading to paresthesia or anesthesia.

Major Spinal Pathways Summary Matrix

A study guide matrix detailing major spinal pathways, what modalities they carry, where they decussate, and their classic clinical deficit patterns.